Polyolefins are a class of polymers derived from simple olefins. Known methods of making polyolefins involve the use of Ziegler-Natta polymerization catalysts. These catalysts polymerize vinyl monomers and/or ethylene using a transition metal halide to provide a polyolefin. Polyethylene is a polyolefin.
Numerous Ziegler-Natta polymerization catalysts exist. The catalysts have different characteristics and/or lead to the production of polyolefins having diverse properties. For example, certain catalysts have high activity while other catalysts have low activity, and similarly certain catalysts have a long life while other catalysts have a short life. Moreover, polyolefins made with the use of Ziegler-Natta polymerization catalysts vary in stereoregularity, molecular weight distribution, impact strength, melt-flowability, rigidity, heat sealability, isotacticity, and the like.
Polyethylene is the most popular plastic in the world. Polyethylene is used to make grocery bags, shampoo bottles, toys, and even body armor. For such a versatile material, it has a very simple structure, the simplest of all commercial polymers. Specifically, a molecule of polyethylene is merely a long chain of carbon atoms, with two hydrogen atoms attached to each carbon atom. Sometimes some of the carbons, instead of having hydrogens attached to them, have long chains of polyethylene attached to them. This type of polymer is labeled branched or low density polyethylene (LDPE). When there is no branching, the polymer is labeled linear polyethylene (HDPE). Linear polyethylene is much generally stronger than branched polyethylene, but branched polyethylene is typically cheaper and easier to make.